This is a continuation of application Ser. No. 13/507,984 filed Aug. 10, 2012.
The following are some prior art that presently appears relevant:
U.S. PatentsPat. No.Issue DatePatentee4,326,520Apr. 27, 1982Alley3,774,605Nov. 27, 1973Jewett3,838,688Oct. 1, 1974May, Wilks